Here, Pinnock’s violin metaphor goes to the interrelationship of the “strings” of Calvinism.

Just as one cannot change the pitch of a single string on the violin without adjusting the others [i.e., because they must be tuned to a common pitch standard for the purpose of harmonious function –bc], so one cannot introduce a major new insight into a coherent system like Calvinian theology without having to reconsider many other issues.

. . .

And here, Pinnock honors Calvin by acknowledging his thoroughgoing logic — all the while pointing up that no humans ought to superimpose systems of thought over God and His will. If we do so presume, we end up walking down a road that gets us nowhere, gets us in trouble, or forces us to make a U-turn.

The first and the best discovery I made was that there was no “horrible decree” at all. Calvin had used this expression in connection with his belief that God in his sovereign good pleasure had predestined some people to be eternally lost for no fault of theirs (Institutes, 3.23). Calvin was compelled to say that because, if one thinks that God determines all that happens in the world (his Augustinian premise) and not all are to be saved in the end (as he believed the Bible taught), there was no way around it. Calvin’s logic was impeccable as usual: God wills whatever happens, so if there are to be lost people, God must have willed it. It was as logically necessary as it was morally intolerable.